Ampacity of 18 gauge wire

I looked at an ampacity table but it was confusing.

Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)

Thanks,
        Andy

On Thursday, September 6, 2018 at 10:05:57 AM UTC-4, Andy wrote:
> I looked at an ampacity table but it was confusing.
> 
> Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)
> 
> Thanks,
>         Andy

For four feet that should be OK.  (I'm not at all an electrician.) 
Heck run a double strand if you are worried about it.  

George H. 

On 9/6/2018 9:05 AM, Andy wrote:
> I looked at an ampacity table but it was confusing.
> 
> Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)
> 
> Thanks,
>          Andy

  I have to assume when you saw 4ft that when we do the calculation we 
need to use 8 ft, because the current flows through both the hot and 
neutral wire.
  18 gauge copper wire has 6.385 ohms of resistance per 1000 ft.
If you divide 8ft by 1000ft you get 125.
  So if we divide 6.385 ohms by 125 we get 0.05108 ohms.
Voltage drop is current times ohms. 10amps x 0.051 = 0.51 volts.
Then from your 120Vac line the ft cord will drop to 119.49 Volts.
  I don't consider that a problem, but note, the manufacturer did!
  What did they use 16 guage?
If you consider a 50ft 18 gauge extension cord, that would cause a
6.385v drop leaving you 113.15v, (you can subtract 0.51 for you 4ft 
cord) starting to have some concern, but it will work unless you put a 
heavy load on the saw. If you put a very heavy load on the saw and draw 
20 amps, now you are down to 106.2v.
  Now start thinking about your home, is there 50 ft of 14gauge wire 
from the breaker box to the outlet. That add another 0.25 ohms in the 
circuit, that will add another 2.5v drop at 10 amps and 5v drop if you 
draw 20 amps.
  Adding all those together and using your 10 amp number,
0.051 + 0.6385 + 0.25 = 0.9395 ohms, you're losing about 1v per amp.
  I hope that gives you some insight.

On 9/6/2018 10:05 AM, Andy wrote:
> ...
> Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)
>

In this situation, it's mostly a matter of heat.  Smaller wires get 
hotter.  And wires in a cable with insulation around them get hotter 
than wires in open air.

In your case, the saw will hardly ever be drawing its full rated load of 
10A = that will happen only when you're really pushing it through thick 
wood.  Also, its use will be intermittent, giving the wire the chance to 
cool between cuts.

So, 18ga is too small for your saw, but you'll probably be OK.

On Thu, 6 Sep 2018 07:05:53 -0700 (PDT), Andy
<andrewkennedy775@gmail.com> wrote:

>I looked at an ampacity table but it was confusing.
>
>Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)
>
>Thanks,
>        Andy

I wouldn't if I were doing it.  But like a lot of things it all
depends on circumstances. (the context)

If you are regularly pulling 10 amps that wire will be getting warm.
Going to rip some longish wood, for instance?  or jam/twist the blade?

It also depends on wire insulation and how resistant it is to melting
or cold flowing if it is pinched while warm.

Copper wire resistance goes up with heat too.

You can never be too safe, and it ain't a lot of money....  You will
probably get away with it, but is that a design goal?

On Thursday, September 6, 2018 at 7:05:57 AM UTC-7, Andy wrote:
> I looked at an ampacity table but it was confusing.
> 
> Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)
> 
> Thanks,
>         Andy

This is a false economy.  You can get a 6 ft 16 gauge extension cord, rated for 13A, from Lowe's for US$1.78 plus tax and interest on your credit card.  My opinion is that for this small amount of money, it is not worth risking your life by being a cheapskate.

On Friday, September 7, 2018 at 9:15:11 AM UTC-5, jf...@my-deja.com wrote:
> On Thursday, September 6, 2018 at 7:05:57 AM UTC-7, Andy wrote:
> > I looked at an ampacity table but it was confusing.
> > 
> > Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)
> > 
> > Thanks,
> >         Andy
> 
> This is a false economy.  You can get a 6 ft 16 gauge extension cord, rated for 13A, from Lowe's for US$1.78 plus tax and interest on your credit card.  My opinion is that for this small amount of money, it is not worth risking your life by being a cheapskate.

Not being a cheapskate. Just frugal.

On 9/7/2018 1:13 PM, Andy wrote:
> On Friday, September 7, 2018 at 9:15:11 AM UTC-5, jf...@my-deja.com wrote:
>> On Thursday, September 6, 2018 at 7:05:57 AM UTC-7, Andy wrote:
>>> I looked at an ampacity table but it was confusing.
>>>
>>> Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)
>>>
>>> Thanks,
>>>          Andy
>>
>> This is a false economy.  You can get a 6 ft 16 gauge extension cord, rated for 13A, from Lowe's for US$1.78 plus tax and interest on your credit card.  My opinion is that for this small amount of money, it is not worth risking your life by being a cheapskate.
> 
> Not being a cheapskate. Just frugal.
> 
Using 18 gauge wire on a circular saw is not recommended. It should be 
on a 15 amp circuit at least. That would mean 14 gauge wire if hard 
wired. If you are using an extension cord I would not go smaller than 16 ga.

On Fri, 7 Sep 2018 10:13:47 -0700 (PDT), Andy
<andrewkennedy775@gmail.com> wrote:

>On Friday, September 7, 2018 at 9:15:11 AM UTC-5, jf...@my-deja.com wrote:
>> On Thursday, September 6, 2018 at 7:05:57 AM UTC-7, Andy wrote:
>> > I looked at an ampacity table but it was confusing.
>> > 
>> > Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circular saw)
>> > 
>> > Thanks,
>> >         Andy
>> 
>> This is a false economy.  You can get a 6 ft 16 gauge extension cord, rated for 13A, from Lowe's for US$1.78 plus tax and interest on your credit card.  My opinion is that for this small amount of money, it is not worth risking your life by being a cheapskate.
>
>Not being a cheapskate. Just frugal.

Then it isn't a matter of design, but one of philosophy.

There is satisfaction in knowing you did the best job you could.  The
way I use my woodworking tools, I don't skimp on how they are
maintained.  I've built stacking wood cases for the hand operated
saws, sanders, grinders, etc.. A lot of effort up-front, but it is
nice to have the wrenches and change-out parts in one place with the
tool, and there's less chance of damage. 

On Friday, September 7, 2018 at 2:21:38 PM UTC-5, Tom Biasi wrote:
> On 9/7/2018 1:13 PM, Andy wrote:
> > On Friday, September 7, 2018 at 9:15:11 AM UTC-5, jf...@my-deja.com wro=
te:
> >> On Thursday, September 6, 2018 at 7:05:57 AM UTC-7, Andy wrote:
> >>> I looked at an ampacity table but it was confusing.
> >>>
> >>> Would a 4 ft. length of 18 AWG wire be ok for a 10 amp load.? (Circul=
ar saw)
> >>>
> >>> Thanks,
> >>>          Andy
> >>
> >> This is a false economy.  You can get a 6 ft 16 gauge extension cord, =
rated for 13A, from Lowe's for US$1.78 plus tax and interest on your credit=
 card.  My opinion is that for this small amount of money, it is not worth =
risking your life by being a cheapskate.
> >=20
> > Not being a cheapskate. Just frugal.
> >=20
> Using 18 gauge wire on a circular saw is not recommended. It should be=20
> on a 15 amp circuit at least. That would mean 14 gauge wire if hard=20
> wired. If you are using an extension cord I would not go smaller than 16 =
ga.

My microwave went out. I salvaged the cord. It was at least 14 gauge.

Andy